1. Field of the Invention
The present invention pertains to apparatus for microsurgery and, in particular, to apparatus which is useful for intraocular surgery which includes removing vitreous from the eye.
2. Description of the Prior Art
The vitreous gel comprises seventy (70) percent of the eye weight and volume and is comprised of ninety-nine (99) percent water and one (1) percent of two main components, collagen fibers and hyaluronic acid, which are bound to large amounts of water. The vitreous owes its characteristic consistency to its sincicial structure in which long collage: chains form the frame for dispersion of hyaluronic acid molecules. This fact and the absence of blood vessels in the vitreous space guarantee the excellent light transmission properties and the inelasticity of the gel. Further, the external surface of the vitreous, called the hyaloid membrane, is a form of densified vitreous gel which is in contact with the following eye structures: the posterior capsule of the crystalline the pars plana epithelium, the retina and the optic nerve.
Alterations of the vitreous prevent light from being normally focused on the retina. Examples of such vitreous alterations are: vitreous bands causing traction and detachment of the retina; vitreous opacification due to the inflammatory or infectious process; the presence of foreign bodies in the vitreous space; eye perforations causing vitreous loss, vitreaous band formations; and many other circumstances. When a surgeon finds it necessary to remove diseased vitreous or other extraneous matter from within the eye, this removal must be accomplished without damage to the retina, to the optic nerva or to their associated blood vessels. This is no easy task as the vitreous cannot be cut by a scalpel or other similar instrumant because it is relatively tough and simply folds over the edge of the knife and refuses to be severed. It is known in the art that one can cut the vitreous gel mechanically using a method wherein two concentric needles, the inner one having a chopping, rotating or oscillating action against the outer tube, cut the vitreous gel and strands. After being cut, the severed vitreous is drawn inside the inner tube by way of suction and, in this way, is removed from the eye.
Many attempts have been made in the art to fabricate apparatus for removing portions of the vitreous humer and/or for cutting vitreous strands in vitreous hemorrhage in order to render the vitreous humer section of the eye transparent. One example of such an apparatus was disclosed in an article by G. A. Peyman and N. A. Dodich entitled "Experimental Vitrectomy," Arch. Ophthal., Vol. 86, Nov, 1971, pp. 548-551 and U.S. Pat. No. 3,776,238 which issued Dec. 4, 1973. The apparatus disclosed in this article and patent consists of two concentric tubes, the outer tube having a hole in the sidewall which forms a mouth near a closed end of the outer tube. The apparatus cuts vitreous as a result of a chopping action of a sharp end of the inner tube against a plain end of the outer tube. The vitreous and strands which are trapped in the tube mouth are chopped and removed through the inner tube by suction applied thereto. The chopping action is caused by oscillating the inner tube within the outer tube, the oscillation being achieved by the action of a solenoid which is affixed to the inner tube. Further, as disclosed, the rate of oscillation of the chopping action can be varied between five and fifty times per second.
A further apparatus for surgically removing vitreous and the like from the eye is disclosed in U.S. Pat. No. 3,815,604 which issued on June 11, 1974. The push-cut apparatus comprises a cylinder having a pneumatically activated piston sliding therewithin. A cutting tube is rigidly fastened to the piston and passes therethrough to a debris-extracting tube. The cutting tube is positioned inside an outer tube and is free to slide therein between physical limits set by a cylinder head and a piston. A narrow slit in the inner tube extends for a considerable length along the tube from a sharp cutting edge. The slit permits the inner tube to be sprung out slightly so that the sharpened end of the inner tube is pressed tightly against the inner surface of the outer tube to ensure, thereby, a good shearing action when the sharp end of the inner tube passes a port opening in the outer tube. The apparatus further includes vent holes for the inside of the housing and means for preventing the piston from rotating with respect to a cap. Vitreous to be severed is drawn into the port opening of the outer tube by suction and is cut off when the piston moves the inner tube so that the sharp end thereof crosses the port of the outer tube. The frequency of traverse of the cutting end of the inner tube across the port of the outer tube is controlled by an electrical circuit which generates timed electrical pulses for controlling air pressure and suction pulses to the piston of the cutting device. This frequency of the pulses may be controlled by a foot-actuated device which is operated by a surgeon employing this apparatus.
A further apparatus for surgically removing vitreous and the like from the eye is disclosed in U.S. Pat. No. 3,884,238 which issued on May 20, 1975. The body or handle of the apparatus comprises a cylinder having a bellows disposed therein. A cutting tube having a sharp end is rigidly fastened to the bellows and is disposed inside an outer tube. The cutting tube is free to slide between physical limits which are manually adjustable. Vitreous to be severed is drawn into a port in the outer tube by suction. This vitreous is cut off when the sharp end of the inner cutting tube is moved across the port of the outer tube. The frequency of traverse of the sharp end of the inner tube across the port of the outer tube is controlled by an electrical circuit which generates timed electrical pulses for controlling air pressure and suction pulses to the piston of the apparatus. This frequency may be controlled by a foot-actuated device which is operated by the surgeon employing this instrument. Air pressure and vacuum are applied to the bellows of the apparatus through a flexible tube and a debris tube is positioned inside of the tube supplying pressure and vacuum.
A further ophthalmic instrument for surgically removing vitreous and the like from the eye is disclosed in U.S. Pat. No. 3,994,297 which issued on Nov. 30, 1976. The apparatus includes a cutting means formed from an inner tube which is slidably carried in an outer tube, i.e., the inner tube reciprocates inside the outer tube. Material to be excised enters a port in the outer tube and is sheared off by the inner tube. The excised material is then removed through the interior portion of the inner tube by a vacuum. The inner tube is rigidly carried by a piston which is driven, in turn, by a pneumatic driver. The pneumatic driver provides pulses of compressed air into a chamber to move the piston. The movement of the piston compresses a spring and the spring returns the piston to a neutral position when the air pulse is no longer present. The apparatus further includes an 0-ring which slidably engages the inner tube in order to prevent the compressed air from escaping therein. The cavity between the inner tube O-ring and the piston is vented to the atmosphere by a passageway to avoid compressing air trapped between the inner tube 0-ring and the piston. Further, vents are used to prevent compression of the air in the spring housing.
A further apparatus for surgically removing vitreous and the like from the eye is disclosed in U.S. Pat. No. 4,011,869 which issued on March 15, 1977. A resilient, inner tubular member is slidably mounted coaxially within a tubular housing. The tubular housing is bent to displace a cutting orifice in the side thereof in a direction toward the resiliant, inner tubular member. As one end of the resilient, inner tubular member passes across the cutting orifice, the inner member is resiliently urged into shearing contact with the cutting orifice. Vitreous matter which is to be severed is drawn into the cutting orifice by a vacuum applied through the inner diameter of the resilient, inner, tubular member. This vitreous matter, including tough fibrous matter approximately one micron thick, is severed by the end of the inner tube as it is driven by a piston across the cutting orifice. In addition, replacement saline solution is introduced into the eye through a further passageway and orifice to prevent collapse of the eyeball. The cutting surfaces of the cutting orifice and the end of the inner tube are inherently self-sharpening due to the resilient urging of one end of the inner tube against the orifice. Further, the self-sharpening effect is enhanced by fabricating the inner member from hard stainless steel and fabricating the tubular housing from fully annealed stainless steel.
A further apparatus for surgically removing vitreous and the like from the eye is disclosed in U.S. Pat. No. 4,577,629 which issued on March 25, 1986. The apparatus includes a cylindrical body having: (1) a vent passageway disposed at one end thereof; (2) front and rear plugs disposed in opposite ends thereof to mount a probe and evacuating and supply tubes; and (3) a piston disposed in a centrally located chamber therein to drive the probe. The front plug, disposed in the front end of the body, has an axial bore therethrough. The piston, disposed in the central chamber, is movable in a reciprocating manner toward and away from the front end; carries sealing rings therearound; and has an axial bore therethrough with a widened portion adjacent to the rear end of the piston. A spring, disposed in the body, engages the front end of the piston to bias the piston away from the front end of the body. The probe includes an elongate tubular outer member having a proximal end secured in the axial bore in the front plug, a closed distal end, and a port adjacent to the distal end. An elongate tubular inner member, slidably disposed in the outer member, has a portion fixed in the axial bore in the piston and a distal end movable across the port to provide a cutting action. The rear plug, disposed in the rear end of the body, has an axial bore therethrough aligned with the probe inner member to permit passage of cut material through the apparatus and a second bore therethrough communicating with the chamber for receiving pressure to move the piston and the probe inner member against the bias of the spring. Evacuating tube means communicates with the probe inner member and a source of suction to draw cut material through the probe inner member. Further, the apparatus can be utilized with any suitable source of suction communicating with the evacuating tube in any suitable pulsed source of pressurized fluid, preferably air, communicating with a supply tube. In addition, the apparatus is particularly well adapted for use with the Ocutome Model 8000 manufactured by CooperVision Incorporated which incorporates a source of suction and a source of pressure capable of supplying pressure pulses at an adjustable frequency of up to 400 pulses per minute or supplying a single pulse upon actuation of a switch to produce a single pulse which corresponds to a single cutting stroke. The suction supplied to the evacuating tube is controlled in conventional manner by a foot-hand operated device coupled with the source of suction.
As one can readily appreciate, the above-mentioned references disclose surgical outting instruments having a tubular outer member and a tubular inner member sliding therein and reciprocated by various means of motive power. These instruments have the disadvantages of not being economically disposable in that they include a number of intricate parts, require precision machining and tooling, require complicated assembly procedures and require disassembly for sharpening and sterilization.
There is a need for surgical outting instruments for cutting and removing vitreous, blood clots, cataracts, lenses and other matter from the eye, as well as for use in other microsurgical procedures. Further, there is a need for such a surgical instrument which: (1) is economically disposable; (2) is inexpensive to fabricate; (3) is easy to use; (4) provides precise cutting and adequate suction and evacuation of cut material; (5) provides a small amount of vibration; (6) is easy to operate; (7) is designed and shaped to facilitate manipulation by a surgeon; and (8) is reliable in operation.